In recent years, electronic timepieces each of which includes a power generating unit for saving efforts of battery changes required in conventional electronic timepieces to enhance the convenience of users and which is driven by power generated by the power generating unit have been developed and commercially available.
In an electronic timepiece including a power generating unit, whether the power generating unit is normally operating or not, whether a path for feeding power generated by the power generating unit to the electronic timepiece is securely connected or not, and so on must be checked in production steps in order to secure basic operations as the power-generating timepiece.
Conventionally, for an electronic timepiece, a technology for outputting micropulses to a motor driver circuit based on a power generation detection signal from a power generation detecting unit in accordance with an operation by an external operating member has been proposed by the present applicant as a unit for performing such functional checks (see Patent Document 1, for example).
Patent Document 1:
WO 02/23285 A1 (Pages 7 to 10 and FIGS. 1 and 19)
The conventional technology will be described below with reference to FIG. 3 of the present application roughly showing a construction of detection of power generation of a power generating unit based on FIGS. 1 and 19 in Patent Document 1.
In the conventional example in FIG. 3, when a state is attained that an external operating member 56 such as the winding knob is pull out, the power generation state of a power generating unit 50 is detected by a power generation detecting unit 52. When the power generating unit 50 is at the power generation state, microcurrent is output from a micropulse generating unit 57 to a motor coil (not shown) through a motor driver circuit (not shown) A checker can check that the power generating unit 50 is generating power by detecting a change in magnetic field occurring in a motor coil upon output of microcurrent through the visual check of movement of an external device such as a second hand attached to a train (both of which are not shown) connecting to a motor or through a tester.
By using this technique, whether a power generating unit is normally operating in a finished timepiece or not and whether the power generating unit and the electronic timepiece are normally connected or not can be checked, and the most basic operations as a power generating timepiece can be secured easily.
Next, problems of the power generation detecting method in conventional examples will be described with reference to FIG. 3.
In a conventional example, the power generating unit 50 and a storage unit 54 are connected directly or through an anti-backflow diode 64. Generally, since the output impedance of the power generating unit 50 exhibits a higher value than that of the internal impedance of the storage unit 54, the voltage occurring across the storage unit 54 exhibits a substantially constant value in accordance with a voltage value output from the storage unit 54 irrespective of the presence of the power generation of the power generating unit 50.
Furthermore, as indicated in ( ) in FIG. 3, when the anti-backflow diode 64 is provided between the power generating unit 50 and the storage unit 54 and while the power generating unit 50 is not generating power, the voltage of the power generating unit 50 is zero (0). On the other hand, while the power generating unit 50 is generating power, the voltage, which is a sum of an amount of a drop in voltage caused when a current value caused when the power generating unit 50 generates power is fed to the anti-backflow diode 64 and a voltage value output from the storage unit 54, occurs across the power generating unit 50.
In both cases, voltage occurring across the power generating unit 50 depends on voltage output from the storage unit 54 and is originally a different value from that of the power generation voltage that the power generating unit 50 generates. According to the conventional technique, the presence of the connection of an electronic timepiece including the power generating unit 50 and storage unit 54 and whether power having a value equivalent to that of voltage output by the storage unit is generated or not could be checked, but whether the power generating unit 50 is generating the originally expected power generation voltage or not could not be checked.
In order to charge electric energy generated by the power generating unit 50 into the storage unit 54, the voltage generated by the power generating unit 50 must be larger than the voltage output from the storage unit 54. However, the storage unit 54 generally tends to have a potential increasing in accordance with an amount of stored power. Therefore, in order to have the storage unit 54 fully charged, the power generation voltage of the power generating unit 50 must be larger than the voltage output when the storage unit 54 is fully charged.
For measurement that satisfies the above-described requirements, an operation of detecting power generation must be performed by detaching the storage unit 54 or by fully charging the storage unit 54. However, in a process for manufacturing an electronic timepiece, the examinations under those states increase the number of man-hours and/or increase the manufacturing costs. In this way, for checking operations of the power generating unit 50, the conventional technology has problems that sufficient examinations cannot be performed or that a large amount of efforts is required for performing sufficient examinations.
It is an object of the invention is to provide an electronic timepiece, which can overcome the above-described defects and can securely check operations of a power generating unit irrespective of the state of a power storage unit.